1. Field of the Invention
The present invention relates to a method for surface treatment of a plastic article and a surface-treated plastic article. In particular, the present invention relates to a surface-treated plastic article exhibiting superior hydrophilicity, that is, wettability, and superior deposition resistance, that is, lipid-fouling resistance, etc., which has been surface-treated without degradation of properties as the plastic article. Specifically, the surface-treated plastic article according to the present invention is appropriately used for contact lenses and intraocular lenses, or medical devices, such as catheters and artificial kidneys.
2. Description of the Related Art
In recent years, plastic articles have been proposed for many purposes. Among those, various plastic articles containing silicon or fluorine have been proposed for contact lenses because of the excellent oxygen permeability.
The plastic articles containing silicon or fluorine are, however, insufficient in wettability, and an improvement in the wettability has been demanded. In particular, various methods have been proposed in order to improve the lens performance (fitting characteristics, comfort etc.) in eyes by surface modification of contact lenses. For example, in U.S. Pat. No. 4,214,014, a method, in which the wettability is imparted to a contact lens by a plasma treatment in an oxygen atmosphere, is disclosed. In JP-A-8-227001, a method, in which the wettability is imparted to a silicone containing hydrogel contact lens by a plasma treatment in the atmosphere of oxygen and/or carbon dioxide gas, is disclosed.
The aforementioned conventional techniques improved the wettability, however, there have been problems in that the material quality of the plastic article was degraded due to the oxygen gas. In addition to this, there was a significant problem in that the wettability varied with time due to washings and a long term of use so as to become hydrophobic.